植物的根系分泌物是植物根系与周围环境之间的化学媒介,通过传递特定的信息,调节根际微环境,影响周围植物的生长。玉米(Zea mays L.)和荞麦(Fagopyrum esculentum Moench)是农作物间套作体系中典型的不能搭配的组合,其障碍因素尚不清楚。以玉米为受体植物,采用根悬空培养的方法,研究了荞麦、高粱(Sorghum bicolor (L.) Moench)根系分泌物对玉米根边缘细胞和根生长的影响。结果发现,玉米根边缘细胞离体培养条件下,用荞麦根系分泌物中的小分子物质处理4、8 h显著诱导边缘细胞凋亡、死亡,细胞活率分别比对照降低了71.6%和72.3%;荞麦根系分泌物中的小分子物质对玉米根产生氧化胁迫,诱导根SOD、POD和CAT活性分别比对照高22.6%、33.9%和107.2%,根中超氧阴离子(O-.2)和脯氨酸含量分别比对照高33.9%和49.8%;荞麦根系分泌物中小分子物质的胁迫使根细胞膜透性增大,与对照相比升高80.0%,丙二醛(MDA)含量比对照升高31.5%;荞麦根系分泌物中小分子物质诱导根内源激素(IAA)含量降低,根系活力下降,根生长受到抑制,与对照比IAA含量降低44.2%,根系活力降低14.4%,根长减少36.9%;高粱根系分泌物对玉米根边缘细胞和根生长无显著的化感胁迫影响。由此可得,荞麦根系分泌物中的小分子物质诱导玉米根边缘细胞凋亡死亡,使其失去边缘细胞的保护作用,进一步诱导根产生氧化胁迫,诱导根内吲哚乙酸(IAA)含量降低,根的生长和发育受到抑制,这可能是玉米荞麦不能间套作的原因所在。
Plant root exudates act as the chemical mediators between root systems and the surrounding environment. Root exudates regulate the rhizosphere microenvironment and affect the growth of nearby plants by transmitting specific information. Zea mays L. (Maize) and Fagopyrum esculentum Moench (buckwheat) are the typically unsuitable combination in intercropping system of crops, however, the obstacle factors are still unclear. In this study, using maize as a recipient plant, the effects of root exudates from buckwheat or Sorghum bicolor (L.) Moench (sorghum) on the root border cells (RBCs) and root growth of maize were investigated by the method of root suspension culture. Results indicated that the viability of RBCs of maize treated with the small molecular substances in the root exudates of buckwheat for 4 and 8 hours decreased by 71.6% and 72.3%, respectively, compared with the control. The small molecular substances in buckwheat root exudates generated oxidative stress on the roots of maize, and the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were 22.6%, 33.9% and 107.2% higher than those of the control, respectively. In addition, the content of the superoxide anion (O-.2) was 33.9% higher than that of the control, while the proline content in the root was 49.8% higher. Furthermore, the small molecular substances in root exudates of buckwheat increased the permeability of root cell membrane by 80.0% and the content of malondialdehyde (MDA) by 31.5% compared with those of the control. The small molecular substances in buckwheat root exudates decreased root endogenous hormone (IAA) content, root activity, and root growth. More specifically, the IAA content decreased by 44.2%, TTC reduction strength decreased by 14.4%, and root length decreased by 36.9%. Sorghum root exudates had no significant allelopathic stress effect on maize root border cells and root growth. Therefore, the small molecular substances in the root exudates of buckwheat can induce the apoptosis and death of maize root border cells, which can make them lose the protective effect of root border cells, further induce the root to produce oxidative stress, reduce the content of IAA in the root, and inhibit the growth and development of the root. We speculate that this is one of the reasons why maize and buckwheat cannot be intercropped.